The present invention relates to light emitting devices. More particularly, the present invention relates to light emitting device modules and lighting devices.
Incandescent light bulb emits visible light when electrical current passes through its resistor wire (typically tungsten) to heat it up till it glows and radiates light. A typical incandescent light bulb emits 22 Lumens of light per watt of energy absorbed by the resistor wire. The resistor wire is eventually burned off after an average of 750 hours. Incandescent light typically produces a spectrum of Red, Green and Blue lights. CRI (Color Rendering Index) is used to describe spectrum of color, 1 being perfect while zero being the worst. Incandescent light has a CRI better than 0.9 while fluorescent is around 0.5-0.7 meaning an object's actual color was 50%-70% illuminated by the light, e.g. a red object may appear to be burgundy rather than its actual red color. HID (High Intensity Discharge) sodium light is amber light that has a very low CRI; as such most colors under its illumination appear to be of different colors.
Fluorescent light is produced by passing electricity to excite mercury vapor inside a vacuum tube to produce UV (Ultraviolet) radiation which in turn causes a phosphor powder coated on the walls of the tube to fluoresce, producing visible light. Fluorescent light bulb produces more light output and last much longer than Incandescent light bulb. But, its disadvantages are low CRI meaning and it contains hazardous chemicals such as mercury which is known to retard brain development in young people or to cause certain cancers. Disposal of Fluorescent light bulb has become an environmental problem in the world today as its hazardous chemicals post serious health threat if the hazardous chemical is air borne and inhaled by human.
HID (High Intensity Discharge) light, also referred to as Arc Lamp, uses electricity to produce electric arc between its tungsten electrodes housed inside a translucent quartz tube that is filled with both gas and metal salts. The arc evaporates the metal salts to form plasma which greatly increase the intensity of light produced by the arc. HID produces more visible light than incandescent and fluorescent lights. However, its disadvantages are similar to fluorescent light as it yields very low CRI and contains hazardous chemicals such as sodium or mercury. Examples are High or Medium Pressure Sodium Light which produce only amber color light that are commonly used to illuminate streets or highways.
Light emitting diode (LED) light bulbs are superior to all of the light bulbs produced by the above light sources. With very fast advance in LED semiconductor chip technology, an LED chip can produce more than 125 Lumens per watt of neutral white light with 80 percent CRI and 100 lumens of warm white light with 90 percent CRI.
Also, LED has a much longer life span than all the other light sources. LED light retains 70 percent of its initial brightness after 50,000 hours of operation under normal conditions. When lighted for 24 hours a day with the usual electrical current, its life span is 10 years.
Approximately twenty percent of the total energy used worldwide is for lighting; and the lights used are incandescent, fluorescent and HID but very few LED at this present moment. As LED light can save at least fifty percent energy used for lighting, it is important to save the world's energy consumption by changing all lights to LED. Potentially, LED can save at least ten percent of the world total energy usage and this is millions of barrels of petroleum or tens of nuclear plants that need to be built in the next few years.
However, because of complexity and difficulties encountered in the design and thermal solution needs to retrofit of LED light source replacing the other light source, adaptation of LED light has been extremely slow. Further, many LED street lights, for example, failed within a year—due to poor thermal design in the fixture—hence scaring off many potential users.
Accordingly, there remains a need for an LED lighting device that can retrofit the existing fixtures and luminaires, to deliver its expected performance and life expectancy, with a much lower initial cost.